Overclocking is an art usually left to the PC — in its simplest form, it's a technique that pushes the components of your computer faster than they're rated for, allowing you to wring out some free performance.

The reason this is possible is that lower speed parts are often higher speed parts that have failed certain tests. After this they are retested at lower speeds until they pass, and are rebranded accordingly — but often this is done with a large safety margin, allowing the end user to push the part near to its original spec simply by tweaking it in the BIOS, or by using a Windows-based overclocking tool.

This is particularly true of CPUs, and lately of Intel CPUs — which of course means the Mac should be overclockable. Except for the bit about there being no BIOS, and seemingly no one has released a native OS X overclocking tool — until now.

ZDNet.de has released such a tool for Mac Pros and Xserves running OS X 10.5, and claims its 2.66GHz Mac Pro reached a stable 3.10GHz, and two of its 2.8GHz Mac Pros were increased to 3.24GHz with little trouble. By comparison, if you opted for dual 3.2GHz quad-core CPUs in your Mac Pro instead of the default dual 2.8GHz quad cores when ordering from the Apple Store, you'd have to fork out an extra AU$2,270. Overclocking the Mac costs? A grand total of AU$0.

It's a simple Front Side Bus overclock, which means other components on the motherboard such as RAM should benefit from the increase as well — however it's not without its side effects, as Apple's engineers clearly never intended on anyone doing this.

For one, the system clock will run faster and internet correction via NTP won't work — the only fix is to restart the Mac. If you rely on scheduling software, this could cause more trouble than it's worth.

There's another problem too — when the computer is woken up from standby mode, it will reset to its original CPU speed, although ZDNet.de is looking to fix this in a future edition.

How far you can push your CPU speed will also depend on the quality of the memory modules your machine has — you may find you're not able to push the overclock as far as ZDNet.de without crashing the system.

Using the tool
Using the tool is simple enough — simply move the slider from left to right to increase the speed of the CPU. Overclocking is best done as a series of steps — if you simply fling the slider all the way to the right in one go, you're sure to crash the machine. Try increasing the speed bit by bit in 10MHz increments. If nothing untoward happens, try increasing it a little bit more. At the point it crashes, you'll have a closer idea of what your machine's limitations are, and can overclock accordingly.

The tool is easy to use — simply slide from left to right.

While we definitely can't recommend this in a production environment where stability is highly important, for home users it can be a great way to wring out that extra bit of performance for zero cost, and a handy way to speed up that slow render. We can only hope Apple won't void warranties for using the tool.

Download it here.